ZCSExchangeMigration stuck

I'm trying to migrate a single user from Exchange to Zimbra.

ZCSExchangeMigrationWizard complains about my SSL certificate on the zimbra server but continues on to 'Source & Dest. Mailboxes.' My real problems start with the Object Picker. It successfully finds users, but when I click OK the users are not getting added to the list of accounts to migrate.

Likewise, no matter how I fool with the Query Builder, I can't get any users into the list to migrate.